Intravascular radiation delivery system

ABSTRACT

An intravascular radiation delivery system including a catheter, a radiation source disposed in an open-ended lumen in the catheter and a closed-ended sheath surrounding the radiation source so as to prevent blood and other fluids from coming into contact with the radiation source. Preferably, the open-ended lumen is centered in the balloon for uniform radiation delivery. The catheter may include a blood perfusion lumen under the balloon or around the balloon. The open-ended lumen in the catheter may have a reduced diameter adjacent the distal end of the catheter to prevent the radiation source from exiting the lumen. Methods of using the radiation delivery system are also disclosed. 
     An alternative method of delivering radiation to a treatment site inside the vasculature of a patient using a gas-filled balloon catheter and a radiation source disposed in the balloon catheter. The treatment site is exposed to radiation, preferably beta radiation, through the gas-filled balloon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.08/782,471 filed Jan. 10, 1997 now U.S. Pat. No. 6,234,951, which is acontinuation-in-part of co-pending U.S. patent application Ser. No.08/608,655 filed on Feb. 29, 1996 now U.S. Pat. No. 5,882,290 entitledINTRAVASCULAR RADIATION DELIVERY SYSTEM, the entire disclosure of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to intralumenal devices used todeliver radiation inside a living body. More specifically, the presentinvention relates to intravascular devices used to deliver radiationinside the vasculature of a patient for therapeutic purposes. Thoseskilled in the art will recognize the benefits of applying the presentinvention to similar fields not discussed herein.

BACKGROUND OF THE INVENTION

Intravascular diseases are commonly treated by relatively non-invasivetechniques such as percutaneous translumenal angioplasty (PTA) andpercutaneous translumenal coronary angioplasty (PTCA). These therapeutictechniques are well-known in the art and typically involve the use of aballoon catheter with a guide wire, possibly in combination with otherintravascular devices. A typical balloon catheter has an elongate shaftwith a balloon attached to its distal end and a manifold attached to theproximal end. In use, the balloon catheter is advanced over the guidewire such that the balloon is positioned adjacent a restriction in adiseased vessel. The balloon is then inflated and the restriction in thevessel is opened.

Vascular restrictions that have been dilated do not always remain open.For example, the restriction may redevelop over a period of time, aphenomenon commonly referred to as restenosis. Various theories havebeen developed to explain the cause for restenosis. It is commonlybelieved that restenosis is caused, at least in part, by cellularproliferation over a period of time to such a degree that a stenosis isreformed in the location of the previously dilated restriction.

Intravascular radiation, including thermal, light and radioactiveradiation, has been proposed as a means to prevent or reduce the effectsof restenosis. For example, U.S. Pat. No. 4,799,479 to Spears suggeststhat heating a dilated restriction may prevent gradual restenosis at thedilation site. In addition, U.S. Pat. No. 5,417,653 to Sahota et al.suggests that delivering relatively low energy light, followingdilatation of a stenosis, may inhibit restenosis. Furthermore, U.S. Pat.No. 5,199,939 to Dake et al. suggests that intravascular delivery ofradioactive radiation may be used to prevent restenosis. While mostclinical studies suggest that thermal radiation and light radiation arenot significantly effective in reducing restenosis, some clinicalstudies have indicated that intravascular delivery of radioactiveradiation is a promising solution to the restenosis enigma.

Since radioactive radiation prevents restenosis but will not dilate astenosis, radiation is preferably administered during or afterdilatation. European Patent No. 0 688 580 to Verin discloses a deviceand method for simultaneously dilating a stenosis and deliveringradioactive radiation. In particular, Verin '580 discloses balloondilatation catheter having an open-ended lumen extending therethroughfor the delivery of a radioactive guide wire.

One problem associated with the open-ended lumen design is that bodilyfluids (e.g., blood) may come into contact with the radioactive guidewire. This may result in contamination of the bodily fluid and requirethe resterilization or disposal of the radioactive guide wire. Toaddress these issues, U.S. Pat. No. 5,503,613 to Weinberger et al.proposes the use of a separate closed-ended lumen in a balloon catheter.The closed-ended lumen may be used to deliver a radioactive guide wirewithout the risk of contaminating the blood and without the need toresterilize or dispose of the radiation source.

The closed-ended lumen design also has draw backs. For example, theaddition of a separate delivery lumen tends to increase the overallprofile of the catheter. An increase in profile is not desirable becauseit may reduce flow rate of fluid injections into the guide catheter andit may interfere with navigation in small vessels.

Another problem with both the open-ended and closed-ended devices isthat radiation must travel through the fluid filled balloon in order toreach the treatment site. While this is not a problem for gammaradiation, it poses a significant problem for beta radiation which doesnot penetrate as well as gamma radiation. Beta radiation is considered agood candidate for radiation treatment because it is easy to shield andcontrol exposure. In larger vessels (e.g., 0.5 cm or larger), a fluidfilled balloon absorbs a significant amount of beta radiation andseverely limits exposure to the treatment site.

SUMMARY OF THE INVENTION

The present invention overcomes these problems by providing a radiationdelivery system that permits the use of an open-ended delivery lumenwithout the risk of blood contamination and without the need to disposeof or resterilize the radiation source. In addition, the presentinvention provides a radiation delivery system that permits betaradiation to be delivered through a balloon without a significantdecrease in radiation exposure to the treatment site, even in largevessels.

One embodiment of the present invention may be described as a catheterhaving an open-ended lumen, a radiation source disposed in theopen-ended lumen of the catheter and a closed-end sheath surrounding theradiation source. The closed-end sheath prevents blood and other fluidsfrom coming into contact with the radiation source so that blood is notcontaminated and the radiation source may be reused. The catheter may bea balloon catheter and may include a guide wire disposed in theopen-ended lumen of the catheter. The open-ended lumen may be afull-length lumen or a partial-length lumen (e.g., a rapid exchangelumen). Preferably, the lumen is centered in the balloon for uniformradiation delivery. The catheter may also include a blood perfusionlumen under the balloon or around the balloon. The open-ended lumen inthe catheter may have a reduced diameter adjacent the distal end of thecatheter to prevent the radiation source from exiting the lumen.Alternatively, the closed-end sheath may have a ridge which abuts acorresponding restriction in the open-end lumen of the catheter toprevent the radiation source from exiting the lumen.

Another embodiment of the present invention may be described as a methodof delivering radiation to a treatment site inside the vasculature of apatient using a the radiation delivery system described above whereinthe method includes the steps of (1) inserting the catheter into thevasculature of a patient; (2) inserting the radiation source into theclosed-end sheath; (3) inserting the radiation source and the closed-endsheath into the lumen of the catheter such that the radioactive portionis positioned adjacent a treatment site; and (3) exposing the vascularwall to radiation from the radiation source. Alternatively, the sheathmay be inserted into the catheter before the radiation source is loadedinto the sheath. The method may also include the steps of (4) removingthe radiation source from the catheter; and (5) removing the catheterfrom the patient. The catheter may be inserted into the vasculature overa guide wire and the guide wire may be removed from the catheter priorto exposing the vascular wall to radiation.

Yet another embodiment of the present invention may be described as amethod of delivering radiation to a treatment site inside thevasculature of a patient using a gas-filled balloon catheter and aradiation source wherein the method includes the steps of: (1) insertingthe catheter into the vasculature such that the balloon is adjacent to atreatment site; (2) inserting the radiation source into the cathetersuch that the radioactive portion is adjacent to the balloon; (3)inflating the balloon with a gas; and (4) exposing the treatment site toradiation from the radiation source through the gas in the balloon. Theballoon may be inflated prior to or subsequent to inserting theradiation source. Preferably beta radiation is used, but otherradioisotopes may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectioned side view of an embodiment of thepresent invention.

FIG. 2 is a cross-sectional view taken at A—A in FIG. 1.

FIG. 3 is a side view of an alternative embodiment of the presentinvention including a helical-shaped balloon.

FIG. 4 is a side view of an alternative embodiment of the presentinvention including a toroidal-serpentine-shaped balloon.

FIGS. 5a, 5 b and 5 c are partially sectioned side views of analternative embodiment of the present invention including arapid-exchange guide wire lumen.

FIG. 6 is a partially sectioned side view of an alternative embodimentof the present invention including a perfusion lumen passing through theballoon.

FIG. 7 is a cross-sectional view taken at B—B in FIG. 6.

FIG. 8 is a cross-sectioned side view of an alternative sheath of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description should be read with reference to thedrawings in which similar parts in different drawings are numbered thesame. The drawings, which are not necessarily to scale, depict exemplaryembodiments and are not intended to limit the scope of the invention.

Examples of suitable materials, dimensions, parts, assemblies,manufacturing processes and methods of use are described for eachembodiment. Otherwise, that which is conventional in the field of theinvention may be implemented. Those skilled in the field will recognizethat many of the examples provided have suitable alternatives which mayalso be utilized.

Refer now to FIGS. 1 and 2 which illustrate a radiation delivery system10 of the present invention. Radiation delivery system 10 includes acatheter 11 having an open-ended lumen 12 extending therethrough. Aclosed-ended sheath 13 surrounds a radiation source 14 (such as a guidewire) disposed in the open-ended lumen 12. An after-loader 22 may beconnected to the proximal end of the radiation source 14 to advance andretract the radiation source 14 and safely contain it when not in use.

The catheter 11 includes an inflatable balloon 15 having an interior 16which is in fluid communication with an inflation lumen 17. The catheter11 illustrated in FIGS. 1 and 2 has a coaxial shaft constructionincluding an inner tube 23 and an outer tube 24. Other shaftconstructions may be employed such as a dual lumen shaft designillustrated in FIG. 6. A manifold 18 is connected to the proximal end ofthe catheter 11 and includes a guide wire port 19 and a flush port 20both of which are in fluid communication with the open-ended lumen 12.The guide wire port may include a toughy-borst (not shown) to seal aboutthe proximal end of the closed-end sheath 13. The manifold 18 alsoincludes an inflation port 21 which is in fluid communication with theinflation lumen 17 and the interior 16 of the balloon 15.

The closed-end sheath 13 preferably extends to the proximal end of thecatheter 11 and may include means for connection to the after-loader 22.The closed-end sheath 13 may be formed of polyethylene, PTFE coatedpolyimide or other suitable flexible material. The closed-end sheath 13may have a length of about 100 to 300 cm depending on the length of thecatheter 11. A wall thickness between 0.0002 and 0.005 inches ispreferred to minimize profile and radiation absorption.

As included with catheter 11 illustrated in FIGS. 1 and 2, theopen-ended lumen 12, closed-ended sheath 13, radiation source 14, afterloader 22 and toughy-borst are also included with catheters 31, 41, 51and 61 as illustrated in FIGS. 3, 4, 5 and 6 respectively. In addition,those skilled in the art will appreciate that the various features ofeach catheter 11, 31, 41, 51 and 61 may be mixed and matched dependingon the desired result. For example, the rapid exchange features ofcatheter 51 may be incorporated into perfusion catheter 61, resulting ina perfusion rapid exchange catheter for the delivery of radiation. Asanother example, the centering balloon 35 or 45 may be contained insideballoon 15 of catheters 11 and 61 to provide a centering function, evenin curved vasculature.

Refer now to FIGS. 3 and 4 which illustrate alternative radiationdelivery catheters 31 and 41. Alternative catheters 31 and 41 may beused in place of catheter 11 for the radiation delivery system 10illustrated in FIG. 1. Except as described herein, the design and use ofalternative catheters 31 and 41 is the same as catheter 11. Alternativecatheter 41 may be made as described in co-pending U.S. patentapplication Ser. No. 08/608,655 which is incorporated herein byreference. Similarly, alternative catheter 31 may be made as describedin the above-referenced case except that the balloon 35 is wound in ahelical shape rather than a serpentine shape.

With reference to FIG. 3, alternative catheter 31 includes ahelically-shaped balloon 35 which is wound around the distal end of thecatheter 31. When the helically-shaped balloon 35 is inflated, ahelically-shaped perfusion path 36 is defined between the balloon 35,the shaft 37 and the inside surface of the blood vessel. The bloodperfusion path 36 allows blood to flow across the treatment site whilethe balloon 35 is inflated. In addition, the concentric and flexiblehelical shape of the inflated balloon 35 maintains the distal portion ofthe catheter 31 centered in the vessel, even around turns in thevasculature. Having the catheter 31 centered in a vessel permits theuniform distribution of radiation to the treatment site.

The distal end of the shaft 37 may include a reduced diameter tip 38with a corresponding reduced inside diameter open-ended lumen (notvisible). The reduced inside diameter permits a conventional guide wireto exit out the distal end of the catheter 31 but prohibits the sheath13 and radioactive source wire 14 from exiting. This assumes, of course,that the sheath 13 or radioactive source wire 14 is larger than theguide wire. A reduced diameter tip may be included on any of thecatheters described herein.

With reference to FIG. 4, alternative catheter 41 includes atoroidal-serpentine-shaped balloon 45. When the serpentine-shapedballoon 45 is inflated, a linear perfusion path 44 is defined betweenthe balloon 45, the shaft 47 and the inside surface of the blood vessel.The blood perfusion path 44 allows blood to flow across the treatmentsite while the balloon 45 is inflated. As with the helical balloondescribed above, the concentric and flexible serpentine shape of theinflated balloon 45 maintains the distal portion of the catheter 41centered in the vessel, even around turns in the vasculature. Having thecatheter 41 centered in a vessel permits the uniform distribution ofradiation to the treatment site. A further advantage of theserpentine-shaped balloon 45 is the relative linearity of the perfusionpath 44 which tends to minimize resistance to blood flow.

Catheter 41 may also include two radiopaque markers 46 to facilitateradiographic placement in the vasculature. The distal end of the shaft47 may include a reduced diameter tip 48 with a corresponding reducedinside diameter open-ended lumen (not visible). The reduced insidediameter permits a conventional guide wire to exit out the distal end ofthe catheter 41 but prohibits the sheath 13 and radioactive source wire14 from exiting.

It is also contemplated that both the helical balloon 35 and theserpentine balloon 45 may be covered with an elastomeric sleeve to aidin collapsing the balloon 35/45 upon deflation. This sleeve would beconnected to the shaft adjacent the proximal and distal ends of theballoon 35/45. It is further contemplated that this sleeve may includeperfusion holes both proximally and distally to permit blood perfusionalong the perfusion path 36/44 defined by the balloon 35/45. If a gas isused to inflate the balloon 35/45 in large diameter vessels (e.g.,peripheral vasculature), it is preferred to not permit perfusion ofblood which would otherwise absorb beta radiation. In such a situation,the sleeve would not include perfusion holes.

Refer now to FIGS. 5a, 5 b and 5 c which illustrate a rapid-exchangeembodiment of the present invention. Alternative catheter 51 may be usedin place of catheter 11 for the radiation delivery system 10 illustratedin FIG. 1. Except as described herein, the design and use of alternativecatheter 51 is the same as catheter 11.

Rapid-exchange catheter 51 includes an elongate shaft 57 with a manifold52 connected to the proximal end and a balloon 45 connected to thedistal end. Although catheter 51 is shown with a serpentine balloon 45and a corresponding linear perfusion path 44, any of the balloon typesdescribed herein may be used.

The manifold 52 includes a balloon inflation port 53 which is in fluidcommunication with the balloon 45 via a conventional inflation lumen. Aradiation source entry port 54 is also included in the manifold 52. Theentry port 54 communicates with the open-ended lumen and permits theinsertion of the sheath 13 and radiation source 14. The open-ended lumenterminates in a reduced diameter tip 58 which permits a conventionalguide wire 56 to exit out the distal end of the catheter 51 butprohibits the sheath 13 and radioactive source wire 14 from exiting.

The guide wire 56 enters the shaft 57 at the proximal guide wire tube55. The guide wire tube 55 is located near the distal end of thecatheter to permit catheter exchange without the need for an extensionwire or wire trapping device. As best seen in FIG. 5c, the guide wiretube 55 has sufficient length such that the guide wire 56 may be pulledback and out of the open-ended lumen. In particular, the distance fromthe proximal end of the guide wire tube 55 to the distal end of thecatheter 51 is less than the length of the guide wire extending outsideof the patient's body. With the guide wire pulled back, the radioactivesource wire 14 and the sheath 13 may be inserted into the entry port 54to the distal end of the catheter 51.

Refer now to FIGS. 6 and 7 which illustrate an alternative perfusioncatheter 61. Alternative catheter 61 may be used in place of catheter 11for the radiation delivery system 10 illustrated in FIG. 1. Except asdescribed herein, the design and use of alternative catheter 61 is thesame as catheter 11.

Perfusion catheter 61 includes an elongate shaft 67 with a manifold 18connected to the proximal end and a balloon 16 connected to the distalend. The shaft 67 is a multi-lumen type extrusion including anopen-ended lumen 62 and an inflation lumen 63. Inflation lumen 63provides fluid communication between the inflation port 21 and theinterior of the balloon 16. Open ended lumen 62 is in communication withentry port 19 for the insertion of a guide wire (not shown) or theradioactive source 14 and sheath 13. A guide wire extension tube 64 isconnected to the distal end of the multi-lumen shaft 67 and rigidlyconnects to the distal end of the balloon 15.

Catheter 61 includes a series of perfusion ports 65 which are in fluidcommunication with the distal portion of the open-ended lumen 62. Theperfusion ports 65 permit blood to flow across the treatment site viathe open-ended lumen while the balloon 15 is inflated.

With reference now to FIG. 8, an alternative sheath 81 is illustrated.Alternative sheath 81 may be used in place of sheath 13 for theradiation delivery system 10 illustrated in FIG. 1. Except as describedherein, the design and use of alternative sheath 81 is the same assheath 13.

Sheath 81 includes a proximal portion 82 and a distal portion 83,wherein the proximal portion 82 includes a relatively thicker wall andlarger outside diameter. The thicker wall tends to absorb radiation toreduce the amount of unwanted exposure, particularly exposure of themedical personnel. The larger outside diameter of the proximal portion84 may be used in conjunction with a corresponding restriction in theopen-ended lumen 12 of any of the catheters described herein.Specifically, the leading edge or ridge 86 of the proximal portion 82may abut a mating restriction in the open-ended lumen 12 such that thesheath 81 cannot be advanced beyond that point. The leading edge 86 andthe mating restriction in the open-ended lumen serve the same functionas the reduced diameter tip described previously and may be used in lieuthereof. In other words, the leading edge 86 and the mating restrictionin the open-ended lumen would permit a conventional guide wire 56 toexit out the distal end of the catheter but would prohibit the sheath 81and radioactive source wire 14 from exiting the distal end of thecatheter.

The closed-end sheath 81 may include means for connection to theafter-loader 22. The closed-end sheath 81 may be formed of polyethylene,PTFE coated polyimide or other suitable flexible material. Theclosed-end sheath 81 may have a length of about 100 to 300 cm dependingon the length of the catheter 11. On the distal portion 83, a wallthickness between 0.0002 and 0.005 inches is preferred to minimizeprofile and radiation absorption. On the proximal portion 82, a wallthickness between 0.040 and 1.0 inches is preferred to maximizeradiation absorption without significantly compromising profile. Theoutside diameter of the proximal portion 82 may be greater than thevascular access size on the portion of the sheath 81 that remainsoutside the body. Once the radiation source is inside the body, the riskof exposure of beta radiation to medical personnel in diminished.

Sheath 81 may also include a radiopaque marker 84 to facilitateradiographic placement of the sheath 81 and radioactive wire 14. Such aradiopaque marker 84 may also be included on sheath 13.

Sheath 81 may also include a series of annular magnets 85. Magnets 85may be used to interact with a series of magnets connected to thecatheter 11, 31, 41, 51 or 61 or a series of magnets connected to aguide catheter (not shown). This general arrangement is described inmore detail in PCT publication WO 95/21566 which is fully incorporatedherein by reference. The interacting magnets provide a means tolongitudinally control and stabilize the position of the radiationsource relative to the patient and treatment site.

In practice, catheters 11, 31, 41, 51 and 61 may be used to deliverradiation to the vascular wall in the following manner. After vascularaccess is established and a guide catheter is in position (if desired),the catheter 11/31/41/51/61 is inserted into the patient with the distalportion adjacent the treatment site. If a guide wire is used, the guidewire may be inserted prior to or simultaneously with the catheter. Theballoon is then inflated to a low pressure sufficient to center theballoon in the vasculature and prevent movement of the catheter relativeto the treatment site. Optionally, the balloon may first be inflated toa higher pressure in order to dilate the treatment site. If desired, theballoon may be inflated with a gas such as nitrogen, carbon dioxide orother non-toxic gas to minimize the absorption of radiation by theinflation media. After dilatation, the balloon is maintained in aninflated state, preferably at a low pressure, to center the catheter inthe vascular lumen. The sheath 13 is placed over the radiation wire 14,preferably ahead of time, and the two are advanced into the open-endedlumen using an after-loader system. Optionally, the sheath 13 is firstloaded into the open-ended lumen of the catheter and the proximal end ofthe sheath is connected to the after-loader, followed by insertion ofthe radioactive source wire 14. The toughy-borst is maintainedsufficiently loose to allow advancement and may be locked to fully sealabout the sheath 13 once the radiation wire 14 and sheath 13 are in thedesired position. If a guide wire is used in the open-ended lumen, theguide wire is preferably retracted to permit passage of the radioactivewire 14 and sheath 13. If a rapid exchange catheter 51 is used, theguide wire is pulled back into the proximal guide wire tube 55. Thevascular wall is then exposed to radiation (preferably beta radiation)for the desired period of time. The radioactive wire 14 and sheath 13are removed from the catheter 11/31/41/51/61 and the catheter is removedfrom the patient.

While the specification describes the preferred embodiments, thoseskilled in the art will appreciate the spirit and scope of the inventionwith reference to the appended claims. Claims directed to methods of thepresent invention may be read without regard as to the order of thesteps unless contraindicated by the teachings herein.

What is claimed is:
 1. An intravascular catheter system, comprising: anelongate catheter including a distally disposed balloon, a radiationsource lumen having an open distal end and a perfusion path, the balloonhaving a non-linear shape and the perfusion path having a linear shape;and an elongate radiation source disposed in the radiation source lumen.2. An intravascular catheter system as in claim 1, wherein the perfusionpath is defined in part by the balloon.
 3. An intravascular cathetersystem as in claim 1, wherein the balloon is gas-filled.
 4. Anintravascular catheter system as in claim 1, wherein the elongateradiation source is disposed in a sheath.
 5. An intravascular cathetersystem as in claim wherein the sheath has a closed distal end.
 6. Anintravascular catheter system as in claim 5, wherein the sheath has awall thickness of between 0.0002 inches and 0.005 inches.
 7. Anintravascular catheter system, comprising: an elongate catheterincluding a distally disposed balloon, a radiation source lumen, theballoon having a non-linear shape; and an elongate sheath disposed inthe radiation source lumen, the sheath having a wall thickness ofbetween 0.0002 inches and 0.005 inches; and an elongate radiation sourcedisposed in the sheath.
 8. An intravascular catheter system as in claim7, wherein the sheath has a closed distal end.
 9. An intravascularcatheter system as in claim 8, wherein the radiation source lumen has anopen distal end.
 10. An intravascular catheter system as in claim 7,wherein the catheter includes a perfusion path.
 11. An intravascularcatheter system as in claim 10, wherein the perfusion path has a linearshape.
 12. An intravascular catheter system as in claim 11, wherein theperfusion path is defined in part by the balloon.
 13. An intravascularcatheter system as in claim 7, wherein the balloon is gas-filled. 14.The intravascular catheter of claim 1, wherein the perfusion path isthin the radiation source lumen.
 15. The intravascular catheter of claim10, wherein the perfusion path is within the radiation source lumen.